1. Field of the Invention
The present invention relates to a semiconductor integrated circuit and an inspection method for its characteristics. More particularly the invention relates to a semiconductor integrated circuit incorporating a characteristic changing circuit which changes characteristic in response to an external signal and to the method of testing characteristic of semiconductor integrated circuit.
2. Description of the Prior Art
As semiconductor technology has advanced it has come possible to integrate circuit elements to a high density on a single semiconductor integrated circuit chip. The composition of the semiconductor integrated circuit is complicated, and circuit elements possessing multiple functions are incorporated into a single semiconductor integrated circuit chip. Such chips are used in various electronic apparatus.
For example, in a semiconductor integrated circuit for processing multiplex voice signal in a television receiver, circuit elements requiring adjustment of characteristic of the circuit elements such as a filter, are often incorporated into a single semiconductor integrated circuit chip. In such a semiconductor integrated circuit, in addition to the input and output terminals necessary for the intrinsic action of this semiconductor integrated circuit, that is, the multiplex voice signal processing action, output terminals for adjustment in order to pick up signals necessary for adjusting the characteristic of the filter are separately provided.
In such semiconductor integrated circuit, it is necessary to provide the output terminals for adjustment in order to sense the filter output that is necessary only in the step of adjusting the filter characteristic, and these output terminals for adjustment occupy a large portion of the limited area of the semiconductor integrated circuit chip and its package leads. In particular, as multiple functions are incorporated into a single semiconductor integrated circuit, the number of input and output terminals has increased, and it is desired to achieve multiple functions by having a small number of terminals.